1. Field of the Invention
Apparatuses consistent with the present invention relate to an antenna device that can be used in a Multiple Input Multiple Output (MIMO) communication system.
2. Description of the Related Art
Multiple Input Multiple Output (MIMO) wireless communication systems have recently attracted attention. MIMO systems are required to enable mobile high-speed data services in wideband mobile communication systems. MIMO indicates an antenna system having a MIMO function. The antenna system can transmit information from each antenna to improve the amount and reliability of transmitted information.
A directivity of an antenna is required to be optimally controlled to increase communication capacity in an MIMO system. There has been suggested a method of disposing a plurality of micro-strip radiators on a dielectric and selecting a micro-strip radiator pointing in a desired direction from the disposed micro-strip radiators by a switch in order to change a directivity of an antenna. However, the directivity is required to be dynamically changed to increase communication capacity. Thus, a method of selecting one from a plurality of micro-strip radiators using a switch complicates the structure of an antenna. Also, if plural antennas are mounted, a distance among the antenna should be about 0.5 λ (wherein λ denotes a wavelength of a transmitted wave) to secure the directivity of each of the antennas. Thus, it is difficult for an antenna device to be compact.
Also, there has been disclosed a structure in which two patch antennas are disposed on both surfaces of a peripheral component (PC) card and one of the two patch antennas is selected to improve communication performance. In this case, the directivity is limited. Thus, the directivity cannot be secured in every possible direction. As a result, it is difficult to secure sufficient communication capacity over all directions in which communication is to be performed.